Burners

ABSTRACT

An oil burner consists of an outer jacket surrounded and spaced from an inner burner tube to provide a surrounding counterflow chamber. Jacket and tube project horizontally inwards from the surrounding combustion chamber wall. Counterflow chamber is substantially closed at both ends. Tube projects inwardly beyond counterflow chamber and terminates in an upfacing burner head. Communication exists at opposite ends of the part of tube surrounded by counterflow chamber. At startup a tongue of flame travels through tube from an injector nozzle. Part of flame counterflows back through surrounding chamber and recirculates through tube. Another part of flame proceeds on to burner head. When parts sufficiently heated, flame in tube is caused to be extinguished and is replaced by hot clear blue flame jets from burner and a multiapertured band in tube within limits of counterflow chamber at end thereof remote from nozzle where counterflow originates. Combustion-supporting air to both chambers adjustably admitted at nozzle end.

BACKGROUND OF THE INVENTION

The present invention relates to oil burners suitable for use in heatinginstallations of various kinds but particularly for those intended foruse in association with domestic heating units and especially domestichot water heating units.

Oil-burning hot-water heaters of the type used in many households areunable to operate efficiently due in part to the design of the burnersthereof and partly because the oil and air which provides thecombustible mixture are both fed to such burners under considerablepressure. The combustion chambers of most domestic burners areconsiderably smaller than those of commercial hot water heaters forexample. As a result of these considerations fuel tends to be sweptthrough these chambers before it can be preheated and mixed thoroughlyas is necessary if a high rate of heat release is to be achieved. Ahigh-pressure burner requires that the combustion chamber associatedtherewith be lined with a refractory material, and to sustain combustionthis material must be incandescent. However since the demand for hotwater is not great or frequent, such burners only operate at fairlywidely spaced intervals and then usually for only a short period oftime. Accordingly, at each time of use the burner should be brought upto an operating temperature which will permit the fuel to burn properly.But length warmup further reduces the effectiveness of such burnersbecause in fact the surrounding refractory material is not brought upproperly to incandescence each time and as a result, conventional hotwater heating equipment and especially conventional domestic hot-waterheating equipment operates considerably below optimum efficiency fromthe standpoint of economy as well as from the standpoint of frequency ofmaintenance which is required to keep an inefficient burner clean.

BRIEF SUMMARY OF THE INVENTION

The invention consists of means for accomplishing the method steps whichare characterized by initially projecting a relatively long jet ortongue of flame from ignited fuel longitudinally from an injectingnozzle assembly to a principal burning zone which is remote therefromand well within (usually substantially centrally within) a surroundingaxially vertical combustion chamber. Simultaneously with what has justbeen stated, a counterflow of a part of said jet or tongue is caused totravel oppositely or back toward the general region from whence theflame emerges from the nozzle assembly, the counterflowing partreturning somewhat as might a fountain having a ring of jets around acentral jet, or as petals might droop from a flower except that the flowhere being referred to is horizontal. The originating location of thecounterflow is between the nozzle assembly or source of flame and theaforesaid principal burning zone. The counterflow is reintroduced backinto the main central jet or tongue near the said source or nozzleassembly.

The next step in the accomplishment of the present invention is that ofseparating the tongue of flame from the nozzle when a sufficient rise inambient temperature has supervened. This separation and extinguishmentof the flame tongue is caused by the turning off of the ignitionelectrode adjacent the aforesaid nozzle. In the action of extinguishmentthe flame leaves the vicinity of the nozzle assembly travelling the fulllength of the burner to appear in the form of a multiplicity of cleanblue uniform flame jets at the mentioned principal burning zone. At thesame time a band of similar clear blue flame jets appears at theoriginating location of counterflow. The principal burning zone isfurther from the nozzle assembly than the originating location ofcounterflow. While the aforesaid main tongue of flame travelshorizontally, the firstmentioned multiplicity of blue flame jets areprojected vertically upwards within the combustion chamber. In theconclusion, in this context, it will accordingly be recognized thatthere is visible within the combustion chamber from the outside thereofafter the burner has been brought up to optimum oil vaporizing heat,only the horizontal upwardly facing disc of blue flame jets.

The novel objects achieved by the burner structure which produces theabove forms of visible heat may be stated as follows:

The burner is designed for consuming any fuel from kerosene to Type 2furnace oil without adjustment. At this point another particular novelfeature of the burner may be stated as residing in the fact that itoperates at atmospheric pressure and requires no forced draft, the onlypoint at which a small quantity of air under pressure is admitted to theburner being at the injection nozzle assembly thereof where suchpressure is in the order of up to 10 p.s.i. as a rule, this beingsubstantially solely for the purpose of breaking up and impellingparticles of oil mixed with air into the burner at the point where thefuel is ignited.

A novel advantage flowing from the last aforementioned objective lies inthe fact that such a burner both starts up and operates at sound levelswhich are low and comparable to existing gas fired units which are wellknown to have acoustic advantages. At the same time, due to its highrecovery rate the present burner would appear to be favorablycompetitive with gas in terms of consumption costs.

A further novel objective achieved by the present burner and alsoflowing from what has already been stated resides in that operation atatmospheric pressure, or in other words, with natural draft, eliminatesone of the biggest service problems which is that of the `linting up` ofoil burners. By this is meant the accumulation of dust and lint upon thefan blades of a forced draft blower, also the accumulation of suchmaterials upon the parts surrounding and adjacent the fan whereby thearea of air entry into the burner is diminished, and also the charringof the burner orifices with lint mixed with incompletely burned oil dueto the slowing down of the fan blades consequent upon the deposit ofsaid lint thereon whereby the air intake capacity is decreased and hencethe combustibility of fuel within the burner.

A yet further novel feature of the present burner arising out of itsquietness of running is its suitability for oil-burning use(particularly when the burner plates are made rectangular instead ofcircular as herein) in association with clamshell heat exchangers asused in automobile trailers, cabin cruisers and the like, which areextremely easy to manufacture and assemble, and are relatively deep,wide, cross-sectionally narrow, and more or less corrugated being fomedof two similar stampings edge joined and between which the burner isplaced usually in multiples of three. .Iadd.

A further important novel object is the provision of means for feedingseparate air to the initial mixing zone between the burner tube and fuelnozzle, and to the combustion chamber so that the two main bodies ofcombustion supporting air may be "balanced" according to atmosphericconditions. These means essentially embody an air distributing housingsecured against the combustion chamber wall so as to cover and encloseboth the air passages to said mixing zone and said combustion chamberwithin a common plenum, the said air passages thus being served from oneair body inside the distributor housing, all to the end of maintainingas nearly as possible a substantially constant volumetric intake of airinto the burner tube regardless of the air pressure (i.e., barometricconditions) in the combustion chamber surrounding the burner so that, inturn, a hot blue flame will be maintained at the burner headsubstantially regardless of barometric combustion chamber variations..Iaddend.

A further objective achieved by the burner consists of efficiencies inthe order of 84 percent combined with the employment of a burningprocess which is nearly perfect, the combustion gases containing onlytraces of CO and no visible smoke or soot. As a result, the low stacktemperature achieved can be advanced to the authorities concerned infavor of permitting the main chimney for such a burner to employ type"B" vents as presently allowed for gas-fired units only.

A further object is to vaporize a tongue of fuel within an inner burnertype by a surrounding counterflow to provide means for preventing itfrom becoming reignited.

Further objectives attained by the present burner reside in the designand arrangement of the same which renders it easily adaptable toreplacement of existing oil-fired burners, quick and easy withdrawal ofthe unit for maintenance purposes and consequent reduction inmaintenance costs, fewness of moving parts thus further simplifyingservicing due to wear-out, the provision of a nozzle the exit orifice ofwhich is very considerably larger than with conventional burnersresulting in a relatively cool nozzle temperature and the elimination ofplugging by dirt and hence carbon buildup while at the same timeproviding a nozzle assembly which is located externally of the fuelcombustion chamber and hence away from the high-temperature zone withits quickly deteriorating effect upon a nozzle, and the production of aflame which does not need a refractory or stainless steel combustionchamber hence resulting in reduced weight, price and maintenance.

Further novel objectives reside in that the purchaser is not obliged tooutlay the expense of a fan or blower and in that a useful space savingis achieved particularly in small housing units due to the eliminationof a fan or blower and associated motor for operating the same.

With the foregoing in view, and such other or further purposes,advantages or novel features as may become apparent from considerationof this disclosure and specification, the present invention consists ofthe inventive concept which is comprised, embodied, embraced, orincluded in the method, process, construction, composition, arrangementor combination of parts, or new use of any of the foregoing, hereinexemplified in one or more specific embodiments of such concept,reference being had to the accompanying Figures in which:

FIG. 1 is a plan representation of the invented oil burner.

FIG. 2 is a sectional elevation substantially on the line 2--2 of FIG.1.

FIG. 3 is an end elevation as viewed from the right of FIG. 2.

FIG. 4 is a plan representation for the purpose of orientating anddepicting in situ the invented oil burner in and with respect to anenclosing combustion chamber.

FIG. 5 is a representation of the flame travel immediately followingstartup.

FIG. 6 is a representation similar to FIG. 5 some 60 to 90 seconds afterstartup.

FIG. 7 is a circuit detail showing an example of a means for causing theflame tongue to be extinguished when a sufficient rise in ambienttemperature is supervened.

In the drawings like characters of reference designate similar parts inthe several Figures.

PRELIMINARY DESCRIPTION

Stated in terms generally consonant with those of the accompany claim orclaims to aid in construing the same the invention includes an innerburner tube A, a surrounding jacket B, said tube and jacket each havingfirst ends C and D respectively, and adjacent second ends E and Frespectively, said jacket being spaced from said tube, a fuel nozzleassembly G, and an ignition electrode H characterized by including (i) aburner head J on the first end of said tube, (ii) means in the form of afirst end wall K (the second end wall being L), the multi-aperturedfirst and second annular bands M and N, and the tube and jacket A and Brespectively defining the surrounding counterflow chamber O, forproviding a counterflow of ignited fuel P (FIG. 5) through saidcounterflow chamber O, said counterflow P being opposite in direction tothe flow, and consisting of a portion of, a tongue Q of flammable fluidprojected through tube A from nozzle assembly G, (iii) the originallocation R of the aforesaid counterflow being between the said nozzleassembly and the said burner head, (iv) means comprising in combinationthe aforesaid second band N and the annular space S for reintroducingcounterflow P back into inner tube A, and (v) means consisting of athermostatic cutout for causing flame tongue Q to be extinguished when asufficient rise in ambient temperature has supervened, andsimultaneously therewith thereby causing the generation of a blue flameT at originating location R and at a principal burning zone U, saidburning zone being further from nozzle assembly G than originatinglocation of counterflow R. .Iadd.Burner tube A encloses a fuel chamberV. Arranged closely around jacket B are air intake apertures X. Coveringand enclosing the pathways of ambient air into both the air and fuelmixing funnel of assembly G and the said apertures X is a variable airdistributing housing Y. .Iaddend.

DETAILED DESCRIPTION

The burner collectively designated 10 is secured to the wall 12 of thesurrounding conventional combustion chamber 14 so as to projecthorizontally into the combustion chamber.

The burner per se comprises, in combination with the aforesaid innerburner tube A, surrounding jacket B, wherein the jacket is spaced fromthe tube, a fuel nozzle assembly G and an ignition electrode H whencharacterized by including the following features:

A first end generally designated 16 and a second end generallydesignated 18, the first end having an imperforate end wall 20 and thesecond having an imperforate second end wall 22. These end walls,together with the jacket B, and the portion 24 of tube A which isbetween said end walls define the aforesaid counterflow chamber O whichis best seen from FIG. 2 to be relatively elongated and of annularconfiguration.

Although it has been said that the end walls 20 and 22 are imperforate,they are nevertheless provided with the central apertures 26 and 28respectively, through the former of which tube A extends, and withsufficient clearance, centrally of said aperture as to provide.Iadd.what is collectively designated as .Iaddend.an annular combustionsupporting structure 30. Second end wall 22 is centrally apertured at 28to provide an intake orifice for the elongated flame tongue Q, afrustoconical funnel 32 being secured to the perimeter of aperture 28upon the external side of chamber 14 to accommodate ignition assembly Gand electrode H.

Burner head J is in the form of an outflared and rimmed formation orsomewhat circular washbasin shaped. Spanning the rim thereof is a pairof slightly spaced multiapertured fuel jet plates 34. Burner tube A isheld centered within jacket B by two discoid rings, one of which isstyled an apertured air distributor 36 slightly spaced from plate 20within chamber O. The other is a flame arrestor plate 38, secured totube A and jacket B as clearly depicted to prevent reignition of theflame of tongue Q after it has been extinguished and vaporized as willhereinafter be explained.

Communication between inner tube A and counterflow chamber O is providedby means of a first annular band 40, a second annular band 42, and anannular space 44. Both annular bands are multiapertured, said aperturesbeing designated 46. Annular space 44 is located between the second endD and second end wall L. A pair of aligned central and relativelyenlarged apertures 48 are provided in jet plates 34. Flanges 50 overlapthe opposite ends of jacket B (which is for all practical purposescoincident with combustion chamber wall 12). Secured upon the externalside of said wall (in other words to the right of said wall as appearsfrom FIG. 2) are adjustable .Iadd.air distributing .Iaddend.meanscollectively designated 52 .Iadd.(including the housing Y) .Iaddend.for.[.varying the admission of.]. .Iadd.a .Iaddend.combustion supportingair .Iadd.stream which flows simultaneously and according to demandthrough the funnel 32 and apertures X .Iaddend.to the interior of tube Aand the surrounding combustion chamber 14 .Iadd.respectively.Iaddend..These means consist of an annular outwardly projecting wall 54 and endplate 56. Wall 54 is provided with a set of spaced .Iadd.air.Iaddend.apertures 58. Overlying wall 54 is a ring 60 provided withapertures of the same size as apertures 58 and capable of registrationor partial registration therewith upon rotation of the ring which isnormally held clamped to wall 54 by means of the conventional nut andbolt bracket assembly collectively designated 62 (FIG. 3).

OPERATION

Upon operation of the associated pump (not shown) air therefrom at 4 to7 p.s.i. enters nozzle assembly G where it creates a partial vacuumthereby attracting oil from the associated oil pump, (also not shown) tobe mixed with said air and expelled through the orifice 28.Approximately on the plane of such orifice electrode H ignites the oiland air mixture to create a long luminous tongue flame commencingsubstantially at the nozzle orifice and extending clear through burnertube A and through burner head J. At the same time an outer annularlayer of the tongue of flame is so to say stripped off and proceedsthrough first annular band 40 into the original location of thecommencement of counterflow R it counterflows through chamber Ooppositely back through flame arrestor plate 38, annularly or radiallyinwards through second apertured annular band 42 as well as throughannular space S to recirculate again toward burner head J within burnertube A.

The just-stated process continues for some 60 to 90 seconds. At thattime ignition electrode H is automatically inactivated. This causes theflame of the tongue Q to be extinguished since it is to be understoodthat under normal operating conditions after some 60 to 90 seconds asufficient rise in ambient temperature has supervened to vaporize theair and oil mixture expelled from orifice G. At the same time aselectrode H is inactivated, a multiplicity of small blue jets of flame64 are established on the outer surface of first annular band 40 as aresult of the intake of .[.fresh.]. air as indicated by arrow 66.[.around the annular combustion supporting.]. .Iadd.through.Iaddend.aperture .[.30.]. .Iadd.26.Iaddend.. Such intake of air is alsodistributed in the narrow annular space 68 between the otherwiseimperforate end plate 20 and perforated distributor ring 36 .[.. Thus.]..Iadd., thus .Iaddend.assisting the completion of combustion not only atthe location R but usefully throughout the entire adjacent region ofcounterflow chamber O and to some extent through the entire chamber.

It is to be understood that by this time the temperature of the burnerhas reached a point where the air and oil mixture is immediatelyvaporized into a gas upon entry past orifice 28. The kinetic energy ofthe nozzle assembly G also draws air as indicated at 70 throughapertures 58 into funnel 32 to mix with the air oil mixture. Inaddition, combustion supporting air also enters through said apertures58 as indicated at 72 for the purpose of aiding the completion ofcombustion within chamber 14. .Iadd.As a result, combustion-supportinginput air in the form of what is herein designated as primary andsecondary air streams 72 and 70 respectively entering the right orsecond end (with respect to FIG. 2) is "balanced across the burner" sothat if for example high barometric stack pressure is obtaining, moreair is admitted to 14 but less to burner tube A so as not to change thecharacter of flame, such as would happen if air were admitted to thetube A proportionately with an increase in negative pressure. It will benoted by best reference to FIG. 2 and the shown openings X and 28therein that the said primary and secondary air streams 70 and 72 areseparate from each other. The intake at aperture 26 may for conveniencebe referred to as a tertiary air stream.

If the burner has been preset for example so as to provide a hot blueflame at or about normal ambient barometric pressure, the performance ofthe air distributing means 52 in the achievement of its object, namelythe maintenance of such a flame regardless of ambient barometricvariation can be described as follows:

Let it be assumed that there is .02 inches of water column negative incombustion chamber 14. Air enters Y through ports 58 and then dividesinto the primary stream 72 to enter 14 through aperture X, and secondarystream 70 to enter the burner tube A by way of funnel 32.

Since the two air streams 70 and 72 are separate, substantially the onlydraw upon 70 is that caused by the aspirating effect of the nozzleassembly G which is invariant. If therefore the barometric pressure incombustion chamber 14 be increased to 0.08 WC negative there is animmediate increase in demand upon the air within the distributinghousing Y. This is satisfied by an increase of air stream 72 throughapertures X at the expense of air stream 70 which is slightly reduceddue to the creation of a small pressure drop between the intake offunnel 32 and the adjacent end plate or wall 56. Thus the combustion airentering housing X due to being split into two streams which areseparate, and led, the one to the combustion chamber 14 and the other tothe burner tube, is automatically balanced resulting in a substantiallyconstant blue flame. This condition would not obtain if the combustionchamber air intake 72 and the burner tube intake 32 each communicatedseparately directly with the surrounding air. In that case by contrastthere would be an equal pressure draw into the combustion chamber andinto the burner tube. Such draw in the case of air stream 70 would bemainly through the burner plate orifices detrimentally changing thecharacter of the flame T. .Iaddend.

During the first 60 to 90 seconds of operation while the flame Q isluminous it will be understood that it is luminous flame which alsocounterflows in chamber O and which proceeds onwardly to and through jetplates 34 including the central spire of flame 74. When vaporizing heathas been achieved, the tongue Q is in the form of a gas and it is as agas that the fuel counterflows backwardly through chamber O as indicatedin FIG. 6. Thus it will be understood that all that is visible whenvaporizing or gasifying heat has been achieved is a ring of blue flamejets T, and an upper facing disc of such jets at the principal burningzone generally designated 76, such disc being horizontal in virtue ofthe generally right-angular disposition of the inner burner tube to thehead J.

When the burner is up to vaporizing heat, the maximum temperaturestested on the upper plate 34 have been 1,100°-1,200° F. However thenormal operating temperatures, reached in 2 to 3 minutes at this placeare 700°-800° F. Between approximately the limits of bracket 78 (FIG. 1)maximum recorded temperatures have been 1,200°-1,400° F. and betweenapproximately the limits of bracket 80 they have been 1,200-1,400°C F.However, the normal operating temperature approximately between thelimits of brackets 78 and 80 are 850°-1,000° F. and 1,000°-1,100° F.respectively and reached in 2 to 3 minutes as aforesaid. In the regionsof the arrows 82 and 84, on the surface of jacket B maximum recordedtemperatures have been 1,100°-1,200° F. and 900°-1,000° F. respectively,and after 2 to 3 minutes, normal temperatures at these two regions areapproximately 900°-1,000° F. and 700°- 800° F. respectively.

From all the foregoing it will now be recognized that the invented oilburner is a low-pressure air-aspirating and atomizing burner. Fuel oilis drawn through the inlet valve of an associated gear-type oil pump anddischarged into the float chamber thereof, which float chamber containsa float-operated oil return control valve. From this float chamber azero pressure regulator is fitted to the nozzle assembly supply line. Avane-type air pump driven by an electric motor common to the oil pumpprovides air at a pressure of approximately 6 p.s.i. to the nozzle. Oilis lifted to the nozzle mixing zone by the aspirating action of theatomizing primary air. As already stated a relatively large nozzle isemployed. The primary air-oil mixture passes through a horizontalpreheating and vaporizing zone being that which has already beendescribed in detail and illustrated in the accompanying drawings beforebeing deflected by a 90° elbow (the angulation between A and J) todischarge across a diffuser plate, or as heretofore designated, theplates 34 where it is ignited. .[.Secondary combustion air.]. .Iadd.Thetertiary air stream 66 .Iaddend. is drawn in concentrically at theaperture .[.30.]. .Iadd.26 .Iaddend.as also already described, about theburner tube A to counterflow chamber O.

In tests, two water heaters fired by the described burner were employed.Efficiency was determined using the indirect method, namely byestablishing an analysis of the flue gases. The apparatus used was thestandard Orsat apparatus capable of measuring the CO₂, CO and oxygen influe gases to a volumetric accuracy of better than 0.2 percent.

Since the Orsat apparatus could not indicate CO of less than 0.1 percentby volume or about 1,000 p.p.m. a more accurate check using BacharachIndustrial Instrument Co. CO Tester was carried out. The results oftesting indicated only traces of CO, in the order of 1 p.p.m.

The fuel used was standard Esso Furnace Oil ASTM Specification D-306Grade No. 2 distillate fuel.

For each of the two heaters tested the apparent variation in efficiencywas found to be well within the possible errors involved in measurementand computation of such efficiency. The variation was less than one-halfof 1 percent from the average. The average efficiency computed forheater No. 1 was 83.8 percent and for heater No. 2 was 83.04 percent.Combustion was found to be complete and evidenced by the practicallyimperceptible traces of CO in the exhaust gases. The gases expelled areCO₂ and water vapor with traces of SO₂ and SO₃ depending on the fuelused. The exhaust gases also were clear and contained no visible smokeor sooty deposits. Here follows the results of the flue gas analysis andthe evaluated efficiencies in respect of heater No. 2:

                     11:04                                                                              11:15                                                                              11:30                                                                              13:05                                                                              13:30                                    Test Number      (d)  1    2    3    4                                        __________________________________________________________________________    Flue gas analysis; (e) percent                                                 CO.sub.2             10.6 10.2 10.4 0.8                                       O.sub.2              6.8  7.8  8.2  7.8                                       CO                   <0.1 <0.1 <0.1 <0.1                                     Temperatures °F.                                                        Ambient         .sup.(1)                                                                           70   72   77   73                                        Stack           .sup.(1)                                                                           390  390  400  400                                       Water in        .sup.(1)                                                                           46   46   46   46                                        Water out       .sup.(1)                                                                           --   140  140  142                                       Excess air percent                                                                            .sup.(1)                                                                           45.3 56.3 61.7 55.9                                      Flue gas loss percent                                                                         .sup.(1)                                                                           8.34 8.52 8.53 9.07                                      Comb. H.sub.2 O loss percent                                                                  .sup.(1)                                                                           7.20 7.19 7.19 7.21                                      Air H.sub.2 O loss percent                                                                    .sup.(1)                                                                           0.14 0.15 0.15 0.15                                      Other loss percent (a)                                                                        .sup.(1)                                                                           1.0  1.0  1.0  1.0                                       Calculated efficiency                                                          percent             83.32                                                                              83.14                                                                              83.13                                                                              82.57                                     Average efficiency   83.04                                                                              83.04                                                                              83.04                                                                              83.04                                    __________________________________________________________________________     .sup.1 Start up of second unit.                                          

In the above table (a) means other loss taken as radiation plusunaccounted for loss, assumed at 1 percent: (d) heater run continuouslyfrom startup. Water flow approximately 3.75 lb./minute: (e) OrsatApparatus accuracy better than 0.2 percent volumetric.

Reverting in conclusion to the burner as exemplified, there is shown inFIG. 7 a means for causing the flame of tongue Q to be extinguished whena sufficient rise in ambient temperature has supervened. The circuitryshown is purely exemplary and not that which is actually used since thecircuitry actually used is considerably complicated beyond what hasherein been shown having regard for other purposes such as demandstartup, safety controls and the like common to oil burnerinstallations. The circuitry of FIG. 7 is however sufficient to indicatea means for the precise purpose just stated and it is to be understoodthat the same will be housed within the control box 86 from which, oradjacently from which projects a conventional probe 88 which could alsobe adapted for use as the means for causing the flame of the tongue tobe extinguished under the circumstances just mentioned, both theutilization of the probe for such a purpose and the circuit of FIG. 7being well within the skill of those versed in the art to which thisinvention pertains.

With the foregoing understood, a grounded heater coil 90 is provided onone side of the electrode circuit 92, as an element in the seriescircuit 94. A shunt 96 to one of a pair of terminals 98 and 100 islocated in the shunt circuit 96. A bimetallic strip thermostat 102 isconnected in the circuit 94. When the heater coil deflects thethermostat from the position shown and out of contact with terminal 98,circuit 92 is interrupted and the electrode H inactivated. As aconsequence the visible tongue of flame is quenched in favour of thecondition which has already been fully described herein.

Various modifications can be made within the scope of the inventiveconcept disclosed. Accordingly, it is intended that what is set forthherein should be regarded as illustrative of such concept and not forthe purpose of limiting protection to any particular embodiment thereof,and that only such limitations should be placed upon the scope ofprotection to which the .[.inventor hereof.]. .Iadd.patentee .Iaddend.isentitled as justice dictates.

What is claimed is:
 1. In the art of combusting flammable fluid fuel forcreating heated gas, the method steps which are characterized by:i.initially projecting a relatively long tongue of ignited fuellongitudinally from a source to a principal burning zone remote fromsaid source, ii. causing an opposite, counterflow of a part of saidtongue back towards said source, the originating location of saidcounterflow being between said source and said principal burning zone,iii. reintroducing said counterflow back into said tongue near saidsource, iv. causing the flame of said tongue to be extinguished when asufficient rise in ambient temperature has supervened, and substantiallysimultaneously therewith v. causing the generation of a blue flame atthe said originating location of counterflow, and at said principalburning zone, and vi. introducing sufficient air to .[.meet therequirements aforesaid, said burning zone being further from said sourcethan said original location of counterflow..]. .Iadd.said burner tosupport combustion..Iaddend.
 2. The method according to claim 1 whichincludes the step of admitting additional counterflow air to mix withsaid first mentioned counterflow. .[.3. The method according to claim 1which is effected within a surrounding combustion chamber and whichincludes the steps of:i. admitting additional counterflow air to mixwith said first mentioned counterflow, and ii. admitting air to saidcombustion chamber from a location near said source to mix with saidtongue of ignited fuel within said combustion chamber..]. .[.4. A fluidfuel burner embodying an inner burner tube, a surrounding jacket, saidtube and said jacket each having a first end and adjacent second ends,said jacket being spaced from said tube, a fuel nozzle assembly, anignition electrode and sufficient air intake means, the foregoing beingcharacterized by including: i. a burner head, on the first end of saidtube, ii. means for providing a counterflow of ignited fuel through acounterflow chamber existing between and by virtue of said tube and saidjacket, said counterflow being opposite in direction to the flow of, andconsisting of a portion of, a tongue of flammable fluid projectingthrough said tube from said nozzle assembly iii. the originatinglocation of said counterflow being between said nozzle assembly and saidburner head iv. means for reintroducing said counterflow back into saidinner tube near said nozzle assembly, and v. means for causing the flameof said tongue to be extinguished when a sufficient rise in ambienttemperature has supervened, and substantially simultaneously therewiththereby causing the generation of a blue flame at the said originatinglocation of counterflow, and at a principal burning zone, said burningzone being further from said nozzle assembly than said originatinglocation of counterflow..].
 5. A fluid fuel burner .[.embodying.]..Iadd.including in combination with .Iaddend.an inner burner tube, asurrounding jacket, said tube and jacket each having a first end andadjacent second ends said jacket being spaced from said tube, a fuelnozzle assembly, an ignition electrode and .[.sufficient.]..Iadd.combustion supporting .Iaddend.air intake means .[., the foregoingbeing characterized by including.]. :i. a burner head .[.on.]. .Iadd.at.Iaddend.the first end of said tube ii. first and second end walls forsaid jacket providing a counterflow chamber therebetween surroundingsaid inner tube, said inner tube admitting fuel at said second end anddischarging it at said first end, iii. said second wall extendingbetween said jacket and inner tube adjacent said nozzle assembly .[.iv.said inner tube being vented to an external side of said chamber at thefirst end of said jacket,.]. v. said first end wall being predominantlyimperforate but .[.sufficiently apertured as to permit.]. .Iadd.havingaperture means for permitting .Iaddend.a limited volume of counterflowair into said surrounding .Iadd.counterflow .Iaddend.chamber, vi. saidinner tube being of greater length than said jacket and projectingthrough an aperture provided therefor in said first end wall, vii. saidinner tube providing communication with said chamber adjacent both saidend walls for the counterflow .Iadd.from .Iaddend.and reintroduction.[.respectively.]., to said inner tube of products of combustion burntwithin said inner tube, viii. said burner head being upon the first endportion of said inner tube which end projects through said first endwall to said external side of said .Iadd.counterflow .Iaddend.chamber.6. The invention according to claim 5 in which said communicationbetween said inner tube and said .Iadd.counterflow .Iaddend.chamberadjacent the first end wall thereof is in the form of an annular bandcomprised of a multiplicity of apertures in said inner tube.
 7. Theinvention according to claim 6 in which said communication between saidinner tube and said .Iadd.counterflow .Iaddend.chamber adjacent thesecond end wall thereof includes an annular space between the second endof said tube and said second end wall. .[.8. The invention according toclaim 6 in which said communication between said inner tube and saidchamber adjacent the second end wall thereof is in the form of anannular band comprised of a multiplicity of apertures in said innertube..]. .[.9. The invention according to claim 8 in which saidcommunication between said inner tube and said chamber adjacent thesecond end wall thereof also includes an annular space between theadjacent end of said tube and said second end wall..].
 10. The inventionaccording to claim .[.9.]. .Iadd.7 .Iaddend.which is also characterizedby the provision of an air intake aperture in said second wall, afrustoconical funnel secured to the rim of said aperture substantiallyon the vertex plane thereof, said fuel nozzle assembly .[.and saidignition electrode.]. projecting into said funnel.
 11. The inventionaccording to claim 10 in which said burner is secured to and projectsinwardly from the wall of a combustion chamber, and .[.adjustable.]..Iadd.air distributing .Iaddend.means on the external side of said wallfor .[.varying the admission.]. .Iadd.balancing the volume .Iaddend.ofcombustion supporting air .[.to.]. .Iadd.between .Iaddend.the interiorof said combustion chamber and .[.into.]. .Iadd.the vicinity of.Iaddend.said .[.funnel through venting.]. .Iadd.combustion tube throughaperturing in said funnel and .Iaddend.in said wall upon the outer sideof said jacket .[...]. .Iadd., all said aperturing being within theconfines of said distributing means. .Iaddend.
 12. The inventionaccording to claim 5 which is also characterized by including amultiapertured air-distributing plate on the counterflow chamber side ofsaid first end wall, slightly spaced therefrom.
 13. The inventionaccording to claim .[.9.]. .Iadd.7 .Iaddend.which is also characterizedby including a multiapertured air-distributing plate on the counterflowchamber side of said first end wall, and slightly spaced therefrom. 14.The invention according to claim 5 in which said burner head ischaracterized by being secured to the fuel discharge end of said innertube, said head being in the form of an outflared and rimmed headformation, and at least one multiapertured fuel jet plate spanning saidrim.
 15. The invention according to claim .[.10.]. .Iadd.7 which is alsocharacterized by the provision of an air intake operature in said secondwall, a frusto-conical funnel secured to the rim of said operaturesubstantially on the vertex plain thereof, said fuel nozzle assembly andsaid ignition electrode projecting into said funnel and .Iaddend.inwhich said burner head is characterized by being secured to the firstend of said inner tube, said head being in the form of an outflared andrimmed head formation and at least one multiapertured fuel jet platespanning said rim.
 16. The invention according to claim 5 in which saidburner head is characterized by being secured to the first end of saidinner tube, said head being in the form of an outflared and rimmed headportion, and a pair of closely spaced and parallel, multiapertured fueljet plates spanning said rim, said burner in situ being axiallyhorizontal with said inner tube horizontal and said burner headgenerally right-angularly disposed with said inner tube axis so thatsaid head formation opens upwardly with the rim thereof lying in ahorizontal plane.
 7. The invention according to claim .[.10.]. .Iadd.15.Iaddend.in which said burner head is characterized by being secured tothe first end of said inner tube, said head being in the form of anoutflared and rimmed head portion, and a pair of closely spaced andparallel multiapertured fuel jet plates.
 18. The invention according toclaim 6 which is also characterized by including a multiaperturedair-distributing plate on the counterflow chamber side of said first endwall, and slightly spaced therefrom.
 19. The invention according toclaim 6 in which said communication between said inner tube and saidchamber adjacent the second end wall thereof includes an annular spacebetween the adjacent end of said tube and said second end wall.
 20. Theinvention according to claim 19 in which said burner is secured to andprojects inwardly from the wall of, a combustion chamber, and.[.adjustable.]. .Iadd.air distributing .Iaddend.means on the externalside of said wall for .[.varying the admission.]. .Iadd.admittingvariable volumes .Iaddend.of combustion supporting air .Iadd.anddistributing said air separately to the vicinity of the second end ofsaid inner burner tube and .Iaddend.to the interior of said combustionchamber .[.and into said counterflow chamber..]. .Iadd...Iaddend. 21.The invention according to claim .[.3.]. .Iadd.1 which is effectedwithin a surrounding combustion chamber and which includes the stepsof:admitting additional counterflow air to mix with said first mentionedcounterflow, and admitting air to said combustion chamber from alocation near said source to mix with said tongue of ignited fuel withinsaid combustion chamber, and .Iaddend.which includes the step ofpreventing the reignition of said tongue by said counterflow after ithas been vaporized by said temperature rise and extinguished.
 22. .[.Theinvention according to claim 4 which includes.]. .Iadd.A fluid fuelburner embodying an inner burner tube, a surrounding jacket, said tubeand said jacket each having a first end and adjacent second ends, saidjacket being spaced from said tube, a fuel nozzle assembly, an ignitionelectrode and combustion supporting air intake means, and including incombination:i. a burner head, on the first end of said tube ii. meansfor providing a counterflow of ignited fuel through a counterflowchamber existing between said tube and said jacket, said counterflowbeing opposite in direction to the flow of, and consisting of a portionof, a tongue of flammable fluid projecting through said tube from saidnozzle assembly, iii. the originating location of said counterflow beingbetween said nozzle assembly and said burner head, iv. means forreintroducing said counterflow back into said inner tube near saidnozzle assembly, and v. means for causing the flame of said tongue to beextinguished when a sufficient rise in ambient temperature hassupervened, and substantially simultaneously therewith thereby causingthe generation of a blue flame at the said originating location ofcounterflow, and at said burner head, and vi. .Iaddend.means forpreventing the reignition of said tongue by said counterflow after ithas been vaporized by said temperature rise and extinguished.
 23. Theinvention according to claim 5 which includes flame arrestor means insaid counterflow chamber for preventing the reignition of said tongue bysaid reintroduced products of combustion after said tongue has beenvaporized by said temperature rise and extinguished.
 24. The inventionaccording to claim 12 which includes an annular apertured flame arrestorplate spanning said counterflow chamber between said tube and saidjacket, said plate being relatively near the second ends of said tubeand jacket, said plate preventing the reignition of said tongue by saidcounterflow after .[.it.]. .Iadd.said tongue .Iaddend.has been vaporizedby said temperature rise and extinguished. .Iadd.
 25. For use incombination with a burner tube adapted and designed to project into acombustion chamber from the enclosure defining said chamber, airdistributing means on the exterior side of said enclosure, saiddistributing means being apertured for air admission and communicationwith:a. the interior of said burner tube, b. said combustion chamber,means for automatically, separately, and simultaneously feeding air intosaid tube and into said combustion chamber according to the relativebarometric demands of said tube and combustion chamber, and means forisolating the proportion of air fed into said combustion chamber againstentry into said burner tube at least in the vicinity of said locationfrom which said burner tube projects into said combustion chamber;saidair distributing means being secured to and projecting outwardly fromsaid enclosure, said enclosure being apertured within the confines ofsaid housing so as to be enclosed thereby and permit the passage of airwithin said distribution housing therethrough into said combustionchamber. .Iaddend..Iadd.
 26. The invention according to claim 25 whichincludes a venturi funnel for a fuel nozzle positioned in saiddistributing housing, said funnel being secured and substantially sealedaround its reduced discharge end against air admission other thanthrough the enlarged intake end thereof, said funnel being substantiallyco-axial with said tube. .Iaddend. .Iadd.
 27. The invention according toclaim 26 in which said funnel is situated substantially central of saiddistributing housing the aperturing in said enclosure being arrangedabout said funnel and spaced therefrom. .Iaddend..Iadd.
 28. Theinvention according to claim 27 in which said air intake housingincludes a surrounding apertured wall secured against and projectingoutwardly from said enclosure and an end plate spanning said aperturedwall, a plenum chamber occupying the space between said apertured wall,said end plate, and the portion of said combustion chamber enclosurebounded by said apertured wall. .Iaddend..Iadd.
 29. The inventionaccording to claim 22 in which said burner projects into a combustionchamber from a location at least near to a portion of the enclosuredefining said chamber, air distributing means on the exterior side ofsaid enclosure, said distributing means being apertured for airadmission thereto and air communication with: a. the interior of saidburner tube, b. said combustion chamber,means for automatically,separately, and simultaneously feeding air into said tube and into saidcombustion chamber from said air distributing means according to thebarometric demands of said combustion chamber, and means for isolatingthe proportion of air fed into said combustion chamber against entryinto said burner tube at least in the vicinity of said location fromwhich said burner tube projects into said combustion chamber..Iaddend..Iadd.
 30. The invention according to claim 5 in which saidburner projects into a combustion chamber from a location at least nearto a portion of the enclosure defining said chamber, air distributingmeans on the exterior side of said enclosure, said distributing meansbeing apertured for air admission and communication with: a. theinterior of said burner tube, b. said combustion chamber,means forautomatically, separately, and simultaneously feeding air into said tubeand into said combustion chamber from said air distributing meansaccording to the barometric demands of said combustion chamber, andmeans for isolating the proportion of air fed into said combustionchamber against entry into said burner tube at least in the vicinity ofsaid location from which said burner tube projects into said combustionchamber. .Iaddend..Iadd.
 31. The invention according to claim 7 in whichsaid burner projects into a combustion chamber from a location at leastnear to a portion of the enclosure defining said chamber, airdistributing means on the exterior side of said enclosure, saiddistributing means being apertured for air admission and communicationwith: a. the interior of said burner tube, b. said combustionchamber,means for automatically, separately, and simultaneously feedingair into said tube and into said combustion chamber according to thebarometric demands of said combustion chamber, and means for isolatingthe proportion of air fed into said combustion chamber against entryinto said burner tube at least in the vicinity of said location fromwhich said burner tube projects into said combustion chamber..Iaddend..Iadd.
 32. The invention according to claim 22 in which saidburner projects into a combustion chamber from a location at least nearto a portion of the enclosure defining said chamber, air distributingmeans on the exterior side of said enclosure, said air distributingmeans being apertured for air admission and communication with: a. theinterior of said burner, and b. said combustion chamber,means forautomatically, separately, and simultaneously feeding air into said tubeand into said combustion chamber according to the barometric demands ofsaid combustion chamber, and means for isolating the proportion of airfed into said combustion chamber against entry into said burner tube atleast in the vicinity of said location from which said burner tubeprojects into said combustion chamber, said air distributing means beingin the form of an apertured air intake housing secured to and projectingoutwardly from said enclosure, said enclosure being apertured within theconfines of said housing to permit the passage of air within saiddistribution housing therethrough into said combustion chamber, saidburner tube lying within the produced boundary of said housing, aventuri channel for a fuel nozzle positioned in said distributinghousing, the reduced end of said funnel lying substantially on the planeof said enclosure, said funnel being secured on said plane andsubstantially sealed around its reduced discharge end against airpassage other than through the enlarged intake end thereof, said funnelbeing substantially co-axial with said tube, said funnel being situatedsubstantially central of said distributing housing, the aperturing insaid enclosure being arranged about said funnel and spaced therefrom,said air intake housing including a surrounding apertured wallprojecting outwardly from said enclosure and an end plate spanning saidapertured wall, a plenum chamber occupying the space between saidapertured wall, said end plate, and the portion of said combustionchamber enclosure bounded by said apertured wall. .Iaddend..Iadd. 33.The invention according to claim 5 in which said burner projects into acombustion chamber from a location at least near to a portion of theenclosure defining said chamber, air distributing means on the exteriorside of said enclosure, said air distributing means being apertured forair admission and communication with: a. the interior of said burner,and b. said combustion chamber,means for automatically, separately, andsimultaneously feeding air into said tube and into said combustionchamber according to the barometric demands of said combustion chamber,and means for isolating the proportion of air fed into said combustionchamber against entry into said burner tube at least in the vicinity ofsaid location from which said burner tube projects into said combustionchamber, said air distributing means being in the form of an aperturedair intake housing secured to and projecting outwardly from saidenclosure, said enclosure being apertured within the confines of saidhousing to permit the passage of air within said distribution housingtherethrough into said combustion chamber, said burner tube lying withinthe produced boundary of said housing, a venturi funnel for a fuelnozzle positioned in said distributing housing, the reduced end of saidfunnel lying substantially on the plane of said enclosure, said funnelbeing secured on said plane and substantially sealed around its reduceddischarge end against air passage other than through the enlarged intakeend thereof, said funnel being substantially co-axial with said tube,said funnel being situated substantially central of said distributinghousing, the aperturing in said enclosure being arranged about saidfunnel and spaced therefrom, said air intake housing including asurrounding apertured wall projecting outwardly from said enclosure andan end plate spanning said apertured wall, a plenum chamber occupyingthe space between said apertured wall, said end plate, and the portionof said combustion chamber enclosure bounded by said apertured wall..Iaddend..Iadd.
 34. A fluid fuel burner including an inner burner tubehaving at a first end thereof a burner head, and a jacket surroundingpart of said tube, characterized in that said jacket has a first endwall and a centrally apertured second end wall, said jacket and endwalls defining a counterflow chamber around said inner tube, said innertube being annularly perforated in the vicinity of said first end walland within the confines of said first and second end walls, said innertube and counterflow chamber being in communication in the vicinity ofsaid second end wall and within the confines of said first and secondend walls, an air distributing housing overlying said second end wall onthe exterior side thereof, means for admitting air into said housing, aventuri funnel within said housing communicating with the interior ofsaid housing and with said second end wall central aperture, said funnelbeing substantially coaxial with said inner tube, an injection nozzlefor pulverized fuel, and aperture means within the confines of saidhousing and communicating between the interior of said housing and thespace surrounding said burner. .Iaddend. .Iadd.
 35. The inventionaccording to claim 5 in which said first end wall is sufficientlyapertured to admit said limited volume of counterflowing air. .Iaddend..Iadd.
 36. The method according to claim 1 which is effected within asurrounding combustion chamber and which includes the steps of admittingair to an air distributing means and dividing said air within saiddistributing means into two essentially enclosed and separate airstreams one of which mixes with said ignited fuel and the other of whichenters said combustion chamber. .Iaddend..Iadd.
 37. A fluid fuel burnerembodying an inner burner tube, a surrounding jacket, said tube and saidjacket each having a first end and adjacent second ends, said jacketbeing spaced from said tube, a fuel nozzle assembly, an ignitionelectrode and combustion supporting air intake means, and including incombination: i. a burner head, at the first end of said tube, ii. meansfor providing a counterflow of ignited fuel through a counterflowchamber existing between said tube and said jacket, said counterflowbeing opposite in direction to the flow of, and consisting of a portionof a tongue of flammable fluid projecting through said tube from saidnozzle assembly, iii. the originating location of said counterflow beingbetween said nozzle assembly and said burner head, iv. means forreintroducing said counterflow back into said inner tube near saidnozzle assembly, and v. means for causing the flame of said tongue to beextinguished when a sufficient rise in ambient temperature hassupervened, and substantially simultaneously therewith thereby causingthe generation of a blue flame at the said originating location ofcounterflow, and at said burner head. .Iaddend..Iadd.
 38. The inventionaccording to claim 15 in which said burner is secured to and projectsinwardly from the wall of a combustion chamber having air venting insaid wall upon the outer side of said jacket and air distributing meanson the external side of said wall enclosing said venting, for admittingcombustion supporting air to (a) the interior of said combustion chamberthrough said venting, and (b) through said funnel to said burnertube..Iaddend.